Friday, July 23, 2010

on a foam core carbon fibre frame

The chassis of Critical Power is a carbon fiber recumbent bicycle also known as a short wheel base, remote steered, front wheel drive lowracer. The frame was constructed from a single piece of carbon fiber sandwich board, then the frame shape was cut-out of the board. The edges were laminated, and the components were installed with aluminum brackets.

D: I could use foam wrapped in carbon fibre.
Different beast though.

Likely to test with plywood (!) frame.

To make sure all attachment points work.

A heat resistant foam would play well with resin-impregnated fibre.

Tuesday, July 20, 2010

I know, sad. I used canvastastic- a free demo version that imitates MS Paint.
Sad thing is that my bud Sanjay let me try Pro Engineer 2000 a few years ago, and I never used it.
I'll still need to learn it before building the Mark I.

OK, so the pic is of the Mark I (version 2) that I wish to build.
The hideous blue squiggly lines represent the general contour of a top/bottom partial fairing.
The grey parts represent the basic frame sans fairing.
I think the lower fairing may be of fiberglass or carbon fiber, and just left attached to the bike frame.
The implied fairing on the nose cone and tail box would just be lycra.
I might use pvc pipe ribs bent in a contour like an umbrella.
The Schlumph bottom bracket drive requires room for the foot to press the button.
A version that allows use of handlebar-mounted shifters would be convenient in some cases.

The fairing has the benefit of keeping the sun and weather and cold away from the rider.
However, a high ambient air temperature plus humidity will cause overheating problems.

I either need air inlets in the fairing, or the option to lower the front half to just above the knees.
Opening a vent in the tip of the nose cone would also remove an air pressure peak point.
I'm not sure how a flat fairing will actually fare in a drag test.

If the fairing is unipiece on top, and can be lowered along with the seat rear to allow a much lower profile, then the bike has
the potential to go very fast downhill with the right drive/ gear hub combo.
This has no practical application for a touring bike.
But if the bike can go that fast, then I would be afraid of crashing.
Then deforming aluminum fairing struts instead of light pvc pipe (for a mockup) would look good.
Also, the idea of the seat back/rucksack on mount securing me with the shoulder straps starts to look good.

Why bother making a short wheelbase with a long wheelbase long wheelbase, but with the pedals out front?
Cargo behind the rider. Good highracer profile. Plays well with a fairing tapering behind the rider.

One I realized the chain-thru-body-tube layout was off centre, a thudbuster could be mounted in a standard fashion in the centre. I am pondering just getting this really wide fat-ass granny seat from the bike shop.

I think in low-fairing/seat-way-back racing mode, that the thudbuster would need to be locked or removed.
The seat, being free floating, would bang on the box frame on top of the rear bike rack.

An Alice pack or other external frame backpack will face a lot of strain at the base, where it mounts to the seat rear apparatus.
I would fear it shearing while riding it. It will likely need to be reinforced considerably.
Note that all cargo must be removed from the alice pack for it to recline greatly.
Alternatively, the box mounted on the rear bike rack would need to be removable.

Can Pantour tire shocks be used to address road vibrations?

D: at 150 for a hub, not so bad.
The main issue is that they preclude stuff like a motor assist hub or a dynamo hub.
Plus I would fear the elastomer would harden in cold temperatures.

One way to address this is to mount the dynamo in the bike frame.
This works better if the chain is laid out internally like the Greenmachine.
And the frame has a suspension point for the rear tire.
Really, an entirely different beast.

Thinking about the idea of an off-centre bike frame mass distribution, I realized that 2 very heavy tubes to the left and right of centre, and just a sheet metal bit to cover the lower chain would keep the weight balanced.
The sheet metal would provide some rigidity.
However, I may still go for 2 on the right housing the chain and one heavy one on the right.
All connected with struts for rigidity.

I don't wish to tinker with 'natural' chainlines, beyond raising it above the front wheel on return.

A motor assist that does not involve the front tire hub could still mesh with the pantour.

Too bad Shimano is sitting on the internal bottom bracket dynamo...

Monday, July 19, 2010

ego blow! calculated watt output for hour on ride

D: stupid Mavic odometer has no instructions on how to calibrate to a 24" MBT tire, grr.
Mavic, you SUCK ASS.

So I've been biking in no-man's-land for speed or distance.

Anyway, I finally tweaked Mapquest to set the path I take from home to King to Heidelberg.
... It wasn't 30km.
It was... um about 15km.
It takes me LESS than an hour. I set the sim at 60mins. More like 55 these days, possibly 53.

The watt output over an hour.... 59.
Midrange accomplished amateur.
What a kick in the cojones that is.
I mean, sure, I can do bench reps with my body, perfect sets of 75 pushups, 20 chinups no prob. And much else.
I'm a generalist.
But amateur?

OK at 10 not 9 mph... about 68 watts.
11mph? 78 watts.
12 - 89.

At 13mph, I reach 100 watts for an hour- out of the limp-wristed sissy league.
Gawd, I have my work cut out for me!
Oie! About 20kph.

I mean, I can CHEAT.
Higher pressure tires. Lighter frame. Hybrid tires. Smooth rear tire. Et al.
But that is just that - cheating.
Not a better athlete. A better bike.

D: My legs run, rollerblade. Heavy squats. Deadlift- almost 500 lbs at 175 lbs!
Not specialized biking legs. Nor disproportionate. Yet.
They're starting to get the same blue veiny my chest got around 30,000 pushups this year.
But not huge yet.

I've seen the 'specialists' Guys with these monster legs grafted, Frankenstein-esque like, onto a tiny torso.
Doesn't seem worth it.
But still - I do wanna cross Canada with my legs.

I suspect I have a lotta hybrid type muscle- can convert between strength and endurance.
Lotsa room for improved vascularity.
More local glycogen storage.
Training to use lactic acid waste byproduct is still a work in progress. I do train hard to discomfort.

And what does the super wonderful science news site Sciencedaily have to say about it?
Arginine plus anti-ox.
Nuts 'n seafood. Good fer ya anyway. Healthy fat profile.
Resistance to exhale results in improved aerobic efficiency.
Coffee megadose good- but only for submax activity.
Also reduces post exercise pain 'n increase glycogen uptake.
Use with care.

Will research more later.

Saturday, July 17, 2010

utah trikes talks about Schlumph mountaindrive, details

Combining the Schlumpf HSD with rear internal hubs
For the ultimate in gearing solutions, we like to combine the Schlumpf HSD with internal hubs in the rear. This provides a super easy-to-shift system that is perfect for triking in mud, water, and snow. We have tested the Schlumpf HSD with the Shimano Nexus 8, Nuvinci CVP, and Rohloff SpeedHub. Note that the high torque of the 27-tooth chainring voids the Rohloff warranty, so you do this at your own risk. Under special circumstances we can fit the HSD with a 34-tooth chainring which brings it closer to Rohloff’s minimum requirement of 36 teeth.

What about efficiency?
Planetary Gears - The main criticism that I ever hear about the Schlumpf drives are the stated efficiency of the drives. According to the latest test the planetary gears are rated at 95-97% efficiency when compared to a chainring. In other words, a 68-tooth chainring would be 3-5% more efficient than the Schlumpf in overdrive. What does this mean? Well, it means that if you could actually find a 68-tooth sprocket and had it on your trike instead of the Schlumpf HSD, you might be able to go a little bit faster.

Riding with the Schlumpf
I ride with the HSD overdrive engaged probably 90% of the time. My lowest gear without downshifting the HSD is about 42 gear inches, which I find to be low enough to handle during the stop and go of my regular commute. Should I ever have to make a sudden stop, or forget to downshift, I always have a bail-out gear by just clicking the shift button.


D: I would not select a gear hub/ S Drive combo that results in the S Drive engaged most of the time.
Not a big deal, but a few % efficiency lost all the time adds up.
Better, I say, to finesse the chainring/cog combo and gear hub/S drive combo to allow near-direct drive engaged as much as possible. The Schlumph drive should only be occasionally engaged.

The potentially wide range of gear inches possible with an S drive means buying an expensive wide gear-inch range gear hub could be a waste of money.
I remain unable to locate any info that suggests the 1.65x drive is any more efficient that the 2.5x drive.
That is the only thing that would change my mind.
Plus the 2.5x range S drive will merely results in a wide area of overlap in gearing - no point at all.

Changing the gears will be simpler but slightly reminiscent of the half-step gearing used in yester-year.

A large # of teeth on the chainring and cog will result in improved efficiency but also a weight penalty. Plus technical difficulties.
D: this remains the benchmark study.

Fussing with the Rohloff min. # os teeth on the chainring is not the salient point here.
That chainring will simply be more efficient, if matched with a similarly larger cog.

E.g. NuVinci 2:1 ratio. 52-36. Or 48-24.
Can the 27 be used?

NOS Campagnolo Super Record 54T chainring *144BCD
US $129.99
End Date: Saturday Jul-24-2010 5:46:46 PDT
Buy It Now for only: US $129.99

D: well it exists.

The Nuvinci is eminently suitable to automatic gear shifting. Combined with the silent aspect, it could carve out a niche.
It should stop trying to compete on a conventional basis with gear hubs.
I'm sure even a 'dummy interface' of cheap and electric vs computerized electronic nature could work.

My design philosophy, as somebody planning to cross Canada on a touring bike, is:
1) always take the weight penalty in exchange for improved efficiency
2) expect a prolonged mid-speed level
3) anticipate the need for a 'killer granny gear' given 1).
This pretty much means a mid-range gear hub with a Schlumph drive.

I'll ask Utah Trikes about whether the 2 high speed S drives have different efficiency.
Not sure why I'd spend an extra 100 on the new Alfine 11-gear if the IM 9-gear plays well with the S drive any way.
Other than that the 400%+ range might be more use by itself prior to the fairing addition and S drive upgrade.

Wednesday, July 7, 2010

fairing design. primers.

Recap: I want a fairing that is PRACTICAL.
That means
1) extends over at least half the length
2) is not on the sides to avoid crosswinds
3) is reasonably light
4) allow cooling air flow

D: How to design air intakes:

I think it's important that the vent be placed in front of the windshield as there is a high pressure zone there caused by the windshield bubble. The vent bleeds off some of this pressure. It also makes it easy to have the air blow on your face, as that's where the most blood vessels are to cool you off.

D: Doesn't this mean just put it at the nose tip.

Some basic "rules" are:

Avoid outside corners and areas of sharp streamwise curvature. Shaving off a few square inches of frontal area by carving a flat spot at the widest point will only increase the drag.

Avoid sudden changes in streamwise curvature. The hemispherical nose butting straight into a zero-curvature cylindrical section is a good example of a bad shape. There will usually be a large velocity spike near the curvature discontinuity, followed by a small separation zone.

Avoid aft-facing steps and air leaks at and behind the maximum-thickness point. The small recirculating zone behind a step might not be able to close in the aft pressure rise and might precipitate large-scale flow separation. Leaking "dead" air into the boundary layer over the pressure rise is very detrimental for the same reason. Minimizing the flow out of wheel cutouts is important. The best place to dump ventilation air flow is out of trailing edge.

The back edge or point does not have to be perfectly sharp. A good rule of thumb is that if the area of the flat base is less than drag_area/4, there will be no drag penalty. A good HPV fairing might have CD = 0.10 based on a frontal area of 5 ft^2, in which case the allowable base area would be 0.10 x 5 / 4 = 0.125 ft^2. This might make the fairing a bit shorter.

Surface finish is important, but there is a threshold roughness height k_min below which there is no further drag reduction. This is given by k_min ~ 4 sqrt(2/Cf) nu / V nu = kinematic air viscosity = 1.4e-5 m^2/s V = local flow velocity (m/s) Cf = local skin friction coefficient ~ 0.025 (nu/VL)^(1/7) L = distance from leading edge (m) For a typical fairing at V = 10 m/s this works out to Cf ~ 0.004, k_min ~ 0.1 mm = 0.005 in, which is not all that smooth -- like the surface of galvanized steel, say. A doped cloth surface is probably close to this threshold. For a speed HPV this roughness threshold would be quite smaller.

As far as "truck suck" or crosswind sensitivity, there is very little that can be done other than reduce the height and side area as much as possible. The "airfoil" shape of the fairing will have little effect.

D: hmm the nose-tip based air intake should try to play well with the top/bottom fairing edge.

. Recumbent Cycling Ontario claims that a recumbent's higher terminal velocity permits speeds 34 percent faster than an upright bike. Recumbent bikes climb slowly because they are heavier and the rider cannot pull up on the handlebars. All other things being equal, a road bike is faster on a hilly course than a recumbent.

Read more: Recumbent Vs. Road Bike Speed |

D: but I'm using it to keep warm and/or keep the sun off/keep cool.
I am north-Euro and will MOULT in noonday sun!

D: I've always thought nosecones and tailboxes look nice and do very little.
They defy the rules of thumb for good physics.

D: right now, I"m thinking the bottom fairing and tirewell shells just stay put as basic construction.
The top part can be removed.
For slow tooling around in hilly offroad conditions, this is a good compromise.
D: - always thought wisil missile was innnovative. Apparently didn't work so well.

I'm imagining an air inlet in the nose tip.

Possibly the front half of the top drops down to just above knees, leaving head exposed. But that makes it all very complex.
Worse yet is if I want the bottom top half to optionally drop down for a 'lowracer' layout - very reclined anyway.
No real pracical reason on a tour bike.
But take off the ALICE pack and recline it on the ammo box 'n you've got yer basic layout for breaking highway speed limits...
Making me think that a crash cage might be a good idea on that layout.
Which would require a long wheelbase for stability.
The gearing is a bugger.

Alfine 408% -11 gear.
18 inch granny gear.
73.44 gear inch top gear.
183.6 with 2.5x Schlumph hyperdrive.

Obviously that is overkill.
A 15" super-granny gear is likely to find much more utility.

I'm waiting on Schlumph about efficiency and the high vs hyper speed options.

speed and watts. e motor/generator assist

D: DO like idea of combo motor/generator.
At night, power lights.
Don't need assist during day? Power electronic device like cellphone or music player.
Need assist- route to motor/generator in drive chain.

I confess that a frame-based suspension makes sense if one embeds a hub of some variety in the frame.

Hmm, solidslot motors weigh in at 18lbs.
Not what I had in mind.

D: since the tetz system has weight from the gearing for it, lot to be said for low speed to start.

thinking for granny gear uphill 'n from start at light or on incline.
so want lotsa torque but very low spin.

not sure what app would have this.

Monday, July 5, 2010

modified mark I 'stretch model' SWB. gear hubs.

D - am on a Mac so don't have access to simple Paint program.
I miss my PC.

Will post pic later.
Was doodling at work with my idea for a short wheel base recumbent.
See 'Mark I'.
Basically a simplified DIY cheap Flevobike GreenMachine knockoff.
With chain to rear tire inside the bike frame itself.
That means gear hubs.

I was looking at the Nuvinci and Imotion 9.
The latest Nuvinci N360 has an impressive 360% range versus the IM9's 340%.
But Nuvinci has always been evasive about efficiency.
And even at 30% lighter, it is still POUNDS heavier than the IM9.
Not sure if the gee-whiz factor could be worth it.

But while looking, I found reference to a new mid-level gear hub, the Alfine 11-gear!
D - I fear we are dealing with 'vapourware' right now.
The gear range doesn't add up, for example.

The numbers don’t add up! The original article says the 11-speed hub has a range of 409% with two 17% jumps and eight 13% jumps. Doing the math, 11 gears and those jumps is only 363.9%.

I played around with the numbers in a spreadsheet, and I had to increase the jumps quite a bit to get to 409%. I ended up with two 20% jumps and eight 14% jumps resulting in 410.7%.

The challenge with gearing for my bent bike layout is
1) must be gear hubs
2) should be cheap and light
3) must have good granny gear for going uphill with the extra weight but
4) can use a very high 'gear inch' at the other end to use the low drag to go fast downhill!
On top of that, ideally the gear hub most efficient 'direct drive' would be in the typical all-day cruising speed for a touring bike.
The Rohloff hub does as much as one hub can do, but is very expensive. It will be lighter than trying to pair a mid-range hub to a Schlumph bottom bracket drive, and likely more efficient.

I have sent an e-mail query to Schlumph about whether their highspeed and hyperspeed x1.65 and x2.5 models have different efficiency.
After all, at x2.5 for their Hyperspeed model, if that is the same efficiency, then I might as well just get the cheaper IM9 hub to go with it.

I thought about it and think the NuVinci only makes sense if silent cycling is a priority.
if so, then I would also pair it with a chainless belted drive.
I talked to the maintenance guys at work and they directed me to Canada Bearings in Kitchener for good industrial belts.
Since a belt would not be the correct length, I would need to use my adjustable frame geometry proposal (see earlier blog).

E.g IM9 340% range x 2.5 SHD. With 18" granny gear base, good range.
E.g. Alfine 11 408% range x 1.65 SH. With " ", good range.
The price ranges from 8-900 bux, circa.
The bike can get by without the Schlumph until I can afford it.
I can tweak the chainring/cog arrangement a bit to make up for it.
STRETCH SWB 'bent bike.

I am not sure why nobody has proposed this. It is not much of a stretch from current designs.
I suggest
1) begin with a standard SWB layout, much like a Bachetta/Greenmachine.
2) extend the rear portion behind the rider's seat.
This is much like an upright cargo bike.
If we begin with a typical 48" wheelbase, adding 12" results in a 60" wheelbase.
This is much like a typical long wheelbase recumbent.
So why bother, you ask?
Drag profile. Fairing design.
I'd like to point out I'm designing the Mark I for crossing canada on.
That means steady mid-speed all-day biking.
It must be a practical road design. It can be plenty stable and not too nimble- like a long wheelbase is good at.
It needs to be resistant to crosswind and 'truck suck'.
It needs some limited offroad capability, primarily the ability to handle some gravel on a road shoulder and some dirt trails.
It needs to carry quite a lot of cargo.

Most recumbents just try to tack cargo on wherever it will fit as an afterthought.
I imagine a dedicated trailer could also make sense. One with a teardrop fairing shape.
I am thinking of what is basically a highracer design. I'll never use a lowracer since the lack of see-and-be-seen with traffic scares the living heck out of me!
So all the cross-section for air resistance is basically above the tires.
So the fairing needs to be above the tires.
The only cross-wind fairing part will be very near the ground - the tires and the lower bike frame. That is it. There is little wind near the ground, plus this will not leverage the bike sideways to make it tilt.
There is NO fairing whatsoever above tire level on the sides.
There IS a fairing top and bottom along the whole length.
Lyrcra can be used to variably improve drag profile on the sides, where there is no fairing.
I am thinking of a coupla spandex bits to simulate a nose cone and tail box, with the option for more in the middle.
Cooling issues require a vent of some variety or tilting fairing that can send more air flow onto the cyclist.

I had initially considered a mesh-seat-back only and solid bottom seat.
But a dedicated touring bike is not a commuting bike.
Mostly I'll be reclined and pedalling, not traffic stop-and-go.
Plus I don't like having a sweaty ASS. Eww.
So now I'm thinking of a one-piece mesh bucket seat.
The suspension - a thudbuster of sorts- I'm proposing isolates the rider from the frame.
Combined with front fork suspension, this mimics a full suspension bike.
Though on bumpy ground, the frame weight will make it catch more air than a full suspension bike would get.
Plus road vibrations disrupting laminar air flow on the fairing is a very real consideration.
Using elastomer shock mounts where the fairing attaches should address this and more cheaply than Pantour wheel hubs.

(I have some space shuttle shock absorbing material lying around from a custom ballistic vest I designed. It was used in orthopedic shoe pads. Not cheap!)

The bottom fairing does have some lycra where the legs must come down.

OK, imagine a SWB bent bike from the top.
You have c. 2/3 width at the pedals.
The shoulders are the widest part. This also means the steering hands are widest.
With a USS steering arrangement, this means that lower down, the fairing must still be wide forward of the torso.
Behind the cyclist we have cargo storage. In my case I will likely use Alice pack or thereabouts as the seat back.
I just take it with me when I get off the bike.
The pack is somewhat narrower than shoulders, as wide as the legs.
Behind that, we continue the gradual taper of width with whatever we wanna attach to a bike rack.
I was thinking I'd like to weld a .50cal ammo box the the bike rack for some sort of secure weather-resistant storage.
This leaves the sides open in theory for either folding baskets or panniers.
With the fabric removed from the alice pack (which needs mesh now to support the back), the seat back can recline as far as the
ammo pack, which it then rests upon at a severe tilt.
If we allow a pivoting fairing arrangement, the fairing can be lowered along with the cyclist.
This has no practical use on a road tour.
It would be strictly be of use to show just how damn fast this thing can go on a track or downhill.
Taken to the logical extreme, this feature in the Mark II III IV and V designs, along with a fold-down seat and steering, allows the fairing to be fully closed like a clamshell. This renders the bike theft-resistant and weather-proof.

OK, so now you should see the benefit of a SWB 'stretch' layout.
Even without a partial fairing, it allows for a lot of cargo storage with a surprisingly good drag profile.
Combined with a partial fairing, the drag profile should be brilliant. For a partial fairing.
I have no interest in a full fairing, other than the adjustable clamshell design I just described above.

I suspect I could tweak the steering properties for around-town commuting by adjusting the front fork angle.
Or incorporating some sort of variable steering I am still trying to figure out.

Presently, I am concerned that the whole bike frame is off centre and weighted to the right.
Using a thicker strut on the left with all the cabling in it would offset this.

I have some ideas about embedding a 12V light electric motor assist/ generator (dynamo ish) in the frame to power consumer electronics on road tours.